scholarly journals A Magnetic-Field-Free Exciton Condensate

Physics ◽  
2018 ◽  
Vol 11 ◽  
Author(s):  
Timo Hyart
Keyword(s):  
Magnetic Field ◽  
Free Exciton ◽  
Exciton Condensate

Optical identification of the exciton–polariton in epitaxial InAs

1996 ◽  
Vol 74 (S1) ◽  
pp. 212-215
Author(s):  
Y. Lacroix ◽  
C. A. Tran ◽  
S. P. Watkins ◽  
M. L. W. Thewalt
Keyword(s):  
Magnetic Field ◽  
Photoluminescence Spectrum ◽  
Magnetic Field Dependence ◽  
Free Exciton ◽  
Spectral Lines ◽  
Optical Identification ◽  
Electron Effective Mass ◽  
Exciton Wave Function ◽  
The Magnetic Field ◽  
Excitonic Recombination

We report optical identification of the exciton–polariton in epitaxial InAs by combined photoluminescence, reflectance, and transmittance spectroscopy. The photoluminescence of these samples showed identifiable spectral lines a thousand times narrower than previously published results from other groups. The measurements were made at 1.4 K and at magnetic fields up to 7 T. Contrary to what is observed in other III–V semiconductors such as GaAs or InP, the free exciton (polariton) is nearly invisible in the photoluminescence spectrum without the application of a magnetic field. We believe that the relatively large residual donor concentration coupled with the large spatial extent of the exciton wave function in this material inhibit the existence of unbound excitonic recombination. Reflectance and transmittance spectroscopy provide very strong evidence that our identification is correct, and the magnetic field dependence yielded values of the electron effective mass and g-factor of (0.026 + 0.002)m0 and −15.3 ± 0.2, respectively, based on this assignment.

Free-exciton energy spectrum in InP in a magnetic field

1976 ◽  
Vol 13 (4) ◽  
pp. 1643-1648 ◽  
Author(s):  
S. B. Nam ◽  
D. C. Reynolds ◽  
C. W. Litton ◽  
T. C. Collins ◽  
P. J. Dean ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energy Spectrum ◽  
Free Exciton ◽  
Exciton Energy

Ion - Carrier Exchange Interaction in Cd1−xMnxS

1986 ◽  
Vol 89 ◽  
Author(s):  
M. Nawrocki ◽  
J. P. Lascaray ◽  
D. Coquillat ◽  
M. Demianiuk
Keyword(s):  
Magnetic Field ◽  
Exchange Interaction ◽  
Valence Band ◽  
Field Model ◽  
Free Exciton ◽  
Mean Field ◽  
Exchange Integral ◽  
Mean Field Model ◽  
Exciton Region ◽  
Type Crystal

AbstractMagnetoreflectivity measurements in Faraday and Voigt geometry in the free exciton region (A, B and C excitons are visible) were performed on Cd0.07Mn0.13S at T=1.6 K for magnetic field up to 5.5 T. An analysis of the results in terms of a mean field model for wurtzite type crystal enabled to determine band parameters Δ1, Δ2, Δ3 and exchange integral for valence band N0ß = -1.8 ± 0.08 eV

Exciton Diamagnetic Shifts and Magnetic Field Dependent Linewidths in Ordered and Disordered InGaP Alloys

2001 ◽  
Vol 692 ◽  
Author(s):  
E. D. Jones ◽  
K. K. Bajaj ◽  
G. Coli ◽  
S. A. Crooker ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Order Parameter ◽  
Free Exciton ◽  
Pulsed Magnetic Field ◽  
Pulsed Magnetic Fields ◽  
Exciton Model ◽  
Field Dependent ◽  
Excitonic Transitions ◽  
Lattice Matched

AbstractWe have measured the diamagnetic shifts and photoluminescence linewidths of excitonic transitions in ordered and disordered In0.48 Ga0.52 P alloys, lattice matched to GaAs, in pulsed magnetic fields at 4 and 76K. The pulsed magnetic field ranged between 0 and 50T. The variations diamagnetic shifts with magnetic field in disordered and weakly ordered samples are considerably smaller than those calculated using a free exciton model. For a given magnetic field, the value of the diamagnetic shifts are found to increase with increasing order parameter. Furthermore, for all samples, the diamagnetic shifts at 76K are larger than at 4K suggesting that the excitons are strongly localized.

scholarly journals Photoluminescence, Magnetospectroscopy, and Resonant Electronic Raman Studies of Heteroepitaxial Gallium Nitride

1999 ◽  
Vol 4 (1) ◽  
Author(s):  
B.J. Skromme
Keyword(s):  
Magnetic Field ◽  
Binding Energy ◽  
Room Temperature ◽  
Free Exciton ◽  
Surface Recombination ◽  
Chemical Vapor ◽  
Hydride Vapor Phase Epitaxy ◽  
Chemical Treatments ◽  
Electronic Raman Scattering ◽  
Donor States

Optical spectroscopy, including low and room temperature photoluminescence (PL), reflectance, PL measurements in high magnetic fields up to 12 T, and resonantly-enhanced electronic Raman scattering (RERS) in zero and high magnetic field, has been used to investigate exciton and impurity states and surface recombination in high quality heteroepitaxial GaN grown on sapphire and SiC. Theoretical finite-difference calculations of the donor states as a function of magnetic field have been carried out for comparison, including the effects of anisotropy in the effective mass and dielectric constant. Up to six residual donor species are observed in material grown by hydride vapor phase epitaxy (HVPE) and metalorganic chemical vapor deposition (MOCVD) from their n=2 and n=3 two-electron satellites observed in PL and by RERS. The donor-related nature of the relevant transitions is confirmed from their magnetic field dependence, and the spectral resolution is improved at high fields. The Si donor level is determined to have a binding energy of about 21 meV from observation of its two-electron satellite in lightly Si-doped HVPE material. The free exciton binding energy is shown to be about 26.4 meV, independent of strain, based on observations of the n=2 free exciton. The room temperature band-edge PL peak is confirmed to be free excitonic in nature, based on its linewidth and on comparison with simple reflectance measurements. Reflectance from the edge of a thick HVPE layer shows clear evidence of A, B, and C excitons obeying the relevant selection rules at both low and room temperature. Surface chemical treatments are shown to have substantial effects on room temperature PL efficiency. Passivation with ammonium or sodium sulfide solutions, in particular, yields increases in PL efficiency by a factor of five to seven over air-exposed surfaces. The passivation effect is stable in air, lasting at least one month.

Magnetic-field strengths from optical polarization data

1967 ◽  
Vol 31 ◽  
pp. 381-383
Author(s):  
J. M. Greenberg
Keyword(s):  
Magnetic Field ◽  
Optical Polarization ◽  
Polarization Data ◽  
Term Model ◽  
Source Of Information ◽  
Field Strengths

Van de Hulst (Paper 64, Table 1) has marked optical polarization as a questionable or marginal source of information concerning magnetic field strengths. Rather than arguing about this–I should rate this method asq+-, or quarrelling about the term ‘model-sensitive results’, I wish to stress the historical point that as recently as two years ago there were still some who questioned that optical polarization was definitely due to magnetically-oriented interstellar particles.

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

Structure in the radiation of the galactic disk

1967 ◽  
Vol 31 ◽  
pp. 355-356
Author(s):  
R. D. Davies
Keyword(s):  
Magnetic Field ◽  
Galactic Disk ◽  
Galactic Magnetic Field ◽  
Measured Polarization

Observations at various frequencies between 136 and 1400 MHz indicate a considerable amount of structure in the galactic disk. This result appears consistent both with measured polarization percentages and with considerations of the strength of the galactic magnetic field.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

Faint Hα Emission in the Corona and Its Relation to the Prominences

1994 ◽  
Vol 144 ◽  
pp. 339-342
Author(s):  
V. N. Dermendjiev ◽  
Z. Mouradian ◽  
J.- L. Leroy ◽  
P. Duchlev
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Essential Role ◽  
Hα Emission

AbstractThe relation between episodically observed in the solar corona faint Hαemission structures and the long lived prominences was studied. Particular consideration was given for cases in which the corresponding prominences had undergone DB process. An MHD interpretation of the phenomenon “emissions froides” (cool emission) is proposed in which an essential role plays the prominence supporting magnetic field.

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